Process and apparatus for drying plastic materials



Jan. 19, 1937- A. o. HURXTHAL 2,0 8,18

PRQCESS AND APPARATUS FOR DRYING PLASTIC MATERIALS Filed May 14, 1935 4 Sheets-Sheet 1 Jan. 19, 1937 A. o; 'HURXTHAL PROCESS AND APPARATUS FOR DRYING PLASTIC MATERIALS Filed May 14, 1955 I 4 Sheets -Sheet 2 Jan. 19, 1937. A. o. HURXTHAL PROCESS AND APPARATUS FOR DRYING PLASTIC MATERIALS Filed May 14, 1955 4 Sheets-Sheet 5 Q N N H; 15 R: :I 2

Jan. 19, 1937. i A. o. HURXTHAL Y 2,063,181

. Filed May '14, 1935 4 Sheets-Shet 4 Patented Jan. 19, 1937 PATENT OFFICE raocnss AND APPARATUS FOR narmo rmsrro MATERIALS Alpheus 0. Hurxthal, Philadelphia, Pa", assignor to Proctor & Schwartz, Incorporated, Philadelphia, Pm, a corporation of Pennsylvania Application May 14, 1935, Serial No. 21,440

12 Claim!- This application constitutes a continuation in part of the applicant's prior applications Serial No. 660,412, filed March 11, 1933 and Serial No. 742,186, filed August 30, 1934.

The invention relates to the drying of plastic or semi-plastic materials, such as magnesium carbonate, copper sulphate, lead arsenate, calcium arsenate, iron blue, lake colors (paint pigments), sulphur sludge, clays, dyestuffs and chemicals in general, as well as other plastic substances. v

One object of the present invention is to provide an improved andsimpllfied apparatus and process for drying materials of the above noted character, with a view of accelerating the drying process, reducing the amount of equipment necessary to effect proper drying, and effecting uniform drying of this kind of material at a uniform rate.

Another object of the invention is to efiect the drying of the material in one or two steps, according to the character of the material, and. wherein initial drying in the latter case, and complete drying in the former case, is eflected by a drum type of drier; and wherein, in the case of two-step drying, the second step is preferably effected by a drier of the type employing perforated endless belt conveyers traveling through an enclosed chamber in which a drying medium is being circulated, or by a. rotary inclined barrel or tumbler type of drier having a drying medium passing longitudinally therethrough, or by any other suitable apparatus.

Another object of the invention is to construct the material-supporting surface of the drier drum in such a manner that the material in mass or bulk form will be converted into strips or pieces having various lengths but wherein all pieces regardless of length will be of uniform cross-section of substantially equal dimensions in all cases when leaving the initial drier, whereby uniform drying in the second step may be readily accomplished on a perforated conveyer by passing air through the-mass of irrregularly disposed pieces of material,

jected to agitation in the preferred form of the invention, to allow the air to pass through the bulk, loss by dust carried away by the drying air is materially reduced.

Another object of the invention is to provide the material-carrying surface of the initial drying drum with circumferential grooves having inwardly converging side walls into which the material is readily pressed and readily removed therefrom in a continuous operation and which provides for close contacting of the material with the walls of the grooves as the material shrinks cross-sectionally during drying.

Another object of the invention is to provide one or more pasting rolls or other tamping means for pressing the material firmly into the circumferential grooves, for attaining the most emcient heat-transferring contact between the material and the walls of the grooves.

In the drying of some material, such, for example, as iron blue and others, the material, immediately upon contacting with the heated walls of the'grooves of the drying drum, puffs up or expands or is otherwise raised out of the grooves and out of contact with the walls thereof immediately after passing under the initial pasting roll, by vapor pressure generated in and around the material in the grooves, in which case it is an object of the present invention to provide one or more repasting rolls or retamping means in tandem relation to the initial pasting or tamping means and in spaced relation thereto circumferentially of the drum, whereby the loosened, pufled or expanded material is pressed back into the grooves,- into eficient heat-transferring contact with the walls thereof.

As the material dries vapor generated therein and escaping therefrom reacts between the walls of the grooves and the material and repeatedly loosens the material from the walls of the grooves, such loosening also being caused or ausmented by the shrinking of the material in the grooves, as produced by the evaporation of the moisture therefrom. It is, therefore, another object of the invention to provide the initial drying apparatus with a more or less elastic belt partially circumventing the drum and movable concurrently with the periphery of the drum, in contact with the outer surface of the material deposited between the side walls of the grooves, whereby the material at all times is held or returned to contact with the walls of the grooves in the most emcient heat-transferring manner.

It is another object or the invention to form the holding belt of a porous material to permit Referring now to the accompanying drawings: Fig. 1 is a diagrammatic longitudinal sectional elevation of one form of apparatus for carrying out the drying process in accordance with the principles of the present invention;

Fig. 2 is a view similar to Fig. 1 showing a different type of apparatus for effecting final drying of the material;

Fig. 3 is an enlarged sectional elevation of the apparatus for effecting the shaping and initial drying of the material;

Fig. 4 is a side elevation of the initial drying and shaping drum, with a portion of one end broken away as on the line 44, Fig. 3;

Fig. 5 is a similar view of the initial pasting drum with the section being taken on the line 5-5, Fig. 3;

Fig. 6 is a fragmentary view of a portion of the drum surface showing the material as it is pressed into the grooves by the initial pasting roll and/or by the repasting roll;

Fig. '7 is an enlarged sectional view taken on the line 'I--T, Fig. 6;

Fig. 8 is a view similar to Fig. 6 but showing the pufllng or loosening of the material in the grooves after passing under the initial pasting roll;

Fig. 9 is a view similar to Fig. 6 showing the material as being broken up into pieces in the grooves by subsequent drying and shrinking of the material and loosened therein by the escape of vapor;

Fig. 10 is an enlarged sectional view taken on the line Ill-l0, Fig. 9;

Fig. 11 is a view similar to Fig. 6 showing the material of Fig. 10 pressed back into contact with the walls of the grooves by the holding belt;

Fig. 12 is a sectional view taken on the line |2-|2, Fig. 11, and showing the holding belt applied to the material in the grooves; and

Fig. 13 shows the use of a plurality of repasting rolls.

As shown in Figs. 1 and 2, the apparatus primarily comprises an initial drying and shaping unit A and a final drying'unit B.

As shown in Figs. 3 and 4, the initial drying unit comprises a hollow drum I consisting of a cylindrical shell 2 and end heads 3 and '4 respectively. The heads 3 and 4 are secured to internal flanges 5 formed on the shell 2 adjacent each of the opposite ends thereof. The flanges 5 are provided with axially extending studs 5 passing through openings 1 in the heads 3 and 4 and on the outer ends of which are threaded nuts 8 by which said heads are rigidly secured to the shell 2.

The heads 3 and 4 are respectively provided with trunnions 9 and i0 which are rotatably mounted in suitable bearings ii and I2 mounted on a suitable frame l3 which may be of any desired construction.

The trunnion 9 in the present instance is hollow and is provided at its inner end with a fluted or otherwise axially apertured bushing l4. At its outer end the trunnion 3 is provided with a threaded plug i5 through which, and the hollow trunnion 9 and the bushing l4, extends a pipe l6. On the inner end of the pipe I6 is an elbow i1 into which is threaded a downwardly projecting extension |8 which terminates slightly above the lower horizontally disposed portion of the inner surface of the shell 2.

The plug 15 forms a part of a rotary pressure head I3 which is provided with a cover 23 having a hollow protuberance or enlargement 2| and within which is a second hollow body 22 into which the outer end of the pipe l3 extends and isrigidly secured.

Communicating with the chamber 22 is an outlet pipe 23 and communicating with the chamber 2| is an inlet pipe 24, through which a heating medium, such as steam, passes into and through the head l9 and plug l5 and from which latter the heatingmedium passes through the trunnion 9, around the pipe I5, and through suitable channels formed in the bushing H, to. the interior of the drum i. Condensation and exhaust from the interior of the drum is carried off through the pipes I3, |8 and 23.

The outer peripheral surface of the drum l is provided with a plurality of circumferential grooves 25 which in the present instance are parallel and continuous.

Intermediate the grooves 25 are annular ribs 28 which are relatively narrow at their outer peripheral edges 21 and which are transversely divergent inwardly, said ribs being relativelyv broader at their bases 23 than at their peripheral edges 21, making the opposite side walls 23 of the grooves 25 inwardly convergent, said grooves being wider at their outer ends than they are at their bases 30, whereby the plastic material when pressed into the grooves 25 is wedged between the side walls 23, 23 and against the base wall 3!] thereof into highly efficient heat-transferring contact with said walls.

Pressing of the material 4!: into the grooves 25 of the drum I is effected by means of a plain surfaced hollow pasting roll 3 i, which is provided with trunnions 32 and 33 rotatably mounted in bearings 34 and 35 carried by the framework |3. The roll 3| is adapted to be heated in the same manner as the drum I, the heating medium and exhaust being carried to and from the initial pasting roll 3| by substantially the same type of mechanism as employed with the drum The axis of the initial pasting roll 3| is arranged substantially parallel to the axis of the drum and the peripheral surface of the pasting roll 3| is normally arranged to roll on the outer edges 21 of the ribs 26 of the drum I.

Adjacent the one side of the initial pasting roll 3| and the top of the drum is a hopper 45 into which the material 1: is placed, in bulk. The rolls l and 3, which are rotated in the direction of the arrows illustrated in Fig. 3, causes the material a: to be carried out of the hopper 43 between the peripheral surfaces of the drum and pasting roll 3|, whereby the said pasting roll forces the material a: into the grooves 25 "in the manner above described, leaving the material in the grooves 25 with the top surfaces 1: of the strips of material substantially flush with the peripheral surfaces 21 of the ribs 26, as shown in Fig. 6.

Some materials being of a more or less spongy character will expand and project or bulge outwardly and slightly above the peripheral edges 21 of the ribs after passing from under the initial pasting roll 3|.

Some materials, for example, iron blue and others, immediately upon passing'from under the initial pasting roll 3|, and due to their coming in contact with the heated surfaces 23 and 33 of the grooves in the drum, will puff up or expand in the manner illustrated at x in Fig. 8, due to expansion of the moisture contained within the material. Such expansion reacting against the surfaces of the grooves loosens the material in the grooves and in some instances has been known to explode and blow the material completely out of the grooves.

Loosening of the material from the walls of the grooves materially decreases the efliciency of the heat transfer from walls of the grooves to the material, and in order to re-establish firm, efficient contact between the material and the walls of the grooves a second or repasting roll 4| is provided, which may or may not be heated as desired, depending upon circumstances and the nature of the material being treated.

Like the initial pasting roll 3|, the repasting roll 4| rolls on the outer edges 27 of the ribs 26 and forces the material .1: down tightly against the base 30 of each groove 25 and wedges the material firmly between the converging walls 29 of said grooves. The material, after passing from under the repasting roll 4|, is substantially in the same condition as in passing under the initial pasting roll 3|, that is, as illustrated in Fig. 6, the puffed expanded condition illustrated at a." in Fig. 8 having been corrected.

The repasting roll 4| is provided with suitable trunniohs which may be mounted in bearings directly carried by the frame H but in order that the repasting roll 4| may be moved out of position when desired, said roll is rotatably mounted at its opposite ends in bearings carried by swing brackets 42, said brackets being pivotally mounted on a cross shaft 43 which in turn is rotatably mounted in the present instance in suitable bearings carried by the framework I3. The repasting roll may be resiliently or rigidly held in contact with the peripheral edges of the ribs and/or the outer surfaces of the strips of material located in the grooves 25, as desired.

The material having been pressed back into efficient heat-transferring contact with the converging side walls and bases of the grooves 25 by the repasting roll 4| immediately begins to dry and in most instances to shrink as the moisture is driven out of the material, such shrinkage taking place in a longitudinal and transverse direction relative to the grooves. Further expansion of the vapors being driven out of the material reacts'against the walls of the grooves and the then solidifying material, causing the material to crack transversely and thereby breaking the otherwise continuous arcuate strips of material up into pieces of various lengths but of uniform cross-section.

Normally the contraction of the material, the breaking up of the material into pieces of various lengths, and the reacting of thevapors between the material and the walls of the grooves would cause the pieces of material to become loosened in the grooves and if unrestricted to assume positions, such as those illustrated at m in Fig. 10. Here again, the material loses firm maximum heat-transferring contact with the walls of the grooves. In the present instance, such loosening and the consequent loss of contact is obviated by the use of a belt 50 which partially circumvents the periphery of the drum l and contacts with the outer surface .12 of the material in the grooves. Preferably, the belt is of a more or less porous nature and is more or less elastic and may be, for example, in the form of a rubberized canvas in which the interstices of the fabric are not completely filled with the rubber or in which the interstices of the fabric may be filled with rubber and perforations formed therein and through the fabric subseage of the material and allowing the material to wedge between the walls and thus obtain the firm heat-transferring contact necessary for efflcient drying of the material.

The belt 50, in the present instance, passes around a roller disposed immediately behind the second or repasting roll 4|, said roll 5| being rotatably mounted in suitable bearings carried by the framework 3. The peripheral surface of the belt roll 5| with the belt 50 thereon may bear directly against the outer edges 21 of the ribs 26 of the drum I but preferably this roll is spaced slightly away from the drum I so that the belt 50, for a relatively short distance, is more or less straight between and tangent to the periphery of the roll 5| and to the outer edges 21 of the ribs 26.

The portion 50a of the belt 50 extends around the lower part of the drum 5| from the roll 5| to a plane substantially coincident with the axis of the roll I, where the belt passes around another roll or a shoe 52, preferably the latter, which extends transversely of the belt and is supported by a cross bar 53 supported by the framework I3. The shoe 52, like the roll 5|, is slightly spaced from the outer peripheral edges 21 of the ribs 26, whereby the belt 50 extends straight for a short distance in tangent relation to the peripheral edges of the ribs 26 and the transverse curvature of the shoe 52.

The above noted arrangement, when the belt 50 is tightened, insures the portion 50a of the belt being pulled tightly against the outer peripheral edges 21 of the ribs 26 and insuring the necessary pressure against the material within the grooves to force the material into firm heat-transferring contact with the walls of the grooves.

From the shoe 52 the belt 50 extends outwardly and downwardly, as indicated at 501) and passes around a roll 54 which is rotatably mounted in suitable bearings carried by the framework l3. From the roll 54 the belt 50 passes around another rotatably mounted roll 55 to a tightening roll 55 which is rotatably mounted in bearings 51 which in turn are slidably mounted on horizontal guideways 58 forming part of or carried by the framework I3.

Any suitable means may be provided for sliding the bearings 51 along the guideways 58 to tighten the belt 50. For example, rods 59 may be provided with threaded ends 60 operating in correspondingly threaded apertures in the hearing blocks 51, said rods being provided with collars 6| disposed between vertically arranged legs of brackets 62 secured to the guideways 58 respectively, said screw rods 59 being provided to suitable handles or hand wheels 63 by which the adjustment of the blocks 51 may be accomplished.

During the passage of the material from the belt-supporting roller 5| to the shoe 52, the material receives its initial drying during which it assumes its uniform cross-sectional shape cor responding to the uniform cross-sectional shape of the grooves 25 for passing on to the next drying step in the final drier B.

In some instances, depending upon the nature of the material and the use to which the material is to be put, no secondary drying is necessary, the material receiving its full drying on the periphery of the drum l.

Due to the fact that the material has been wedged continuously between the converging side walls of the grooves 28 the material as it reaches the shoe 52 is frequently so firmly wedged in the grooves that some means must be provided for extracting the material from the grooves and for this purpose, in the present instance, a series of relatively thin flexible blades or needles 85 are arranged with their ends 88 disposed in the grooves 25 and with their outer ends mounted in a cross bar 81 carried by or rotatably mounted on the framework I8, or any other suitable means may be provided for removing the material from the grooves.

After discharging from the grooves 25 of the drum l, the material will pass down on and with the inclined portion 58b of the belt 58, to be discharged on to a suitable conveyer for con- .ducting the material away from the apparatus or for discharging .the material on to or into the conveyer or 'barrel of the secondary drier B, or in the case of a rotary drier for discharging the material into a feed hopper at the high end of the inclined rotary bell.

The drum l, the pasting roll 3|, the repasting roll II and the belt roll 5| or 54 may be driven in peripheral synchronization by any suitable means without departing from the spirit of the invention.

As the drum l rotates in the direction of the arrow, Fig. 3 the broken-off portions 29-19 of the strips :z: -:i: of the material in each of the grooves 25 as shown in Fig. 11, are discharged over and by that portion 50b of the belt 50 passing around the guide roll 54, the broken pieces of material falling into a receiving hopper 88 which is adapted to feed the partially dried lumps of material into the final drier B.

As shown in Figs. 1 and 2, the final drier may be either of the straight-run conveyer type or it may be of the rotary barrel orkiln type of drier. In the instance of Fig. 1, the final drier B is shown as being of the type comprising 'a straight-run perforated conveyer, illustrated at. 10, passing around suitable drums or sprockets 1i and I2 disposed respectively at the feed and delivery ends of the conveyer. The hopper 58 in such instances delivers the material directly onto the upper carrying run 1.811 of the conveyer, whereby said run, moving in the direction of the arrow, Fig. 1, carries the material through a drying chamber 14 formed within and by an outer casing 15 of any suitable construction.

Any suitable means may be provided for circulating air within the chamber 14 and for heating the air in circulation either within or externally of said drying chamber, said circulation being created as by one or more fans diagrammatically illustrated at 18 in Fig. 1.

With the above noted construction, it is possible to effect rapid initial drying, shaping and setting of the plastic material in the grooves 25 of the drum I, by maintaining relatively high temperature within the drum I, the heat from the hollow interior of the drum being transferred to the material carried on and by the drum through the peripheral wall of the drum and the circumferential fins 28 on and pro- ,iecting outwardly from the periphery of the drum, which provides for direct heat-transferring contact with the material disposed within the grooves 25 of the drum, whereby a drum of relatively small diameter and revolving at a fairly high rate of speed will sufllce to effect the initial drying necessary to solidify and set the shape of the material preparatory to itspassing onto the feed end of the conveyer 18 by which the material is conveyed through the final drying unit B.

The final drying may be effected at a relatively lower rate of speed of the conveyer 18 with respect to the surface speed of the drum I and the material having been solidified and formed into pieces of uniform cross-section on the drum I may be'piled haphazardly on the conveyer l8 in a fairly thick layer, the irregular spreading of the pieces of material on the conveyer providing the necessary spaces between such pieces for the passage of the air circulated through the layer of material in the drying chamber 14. a

The air may be, circulated transversely of the conveyer and the chamber 14 or vertically through the layer of material and through the conveyer 18 in which latter case the conveyer would be of suitable foraminous construction. If desired, the chamber 14 may be subdivided transversely to provide, first, a final drying of the material and subsequently a chamber for eflecting cooling or other conditioning of the material.

In the case of the rotary drier illustrated in Fig. 2, the hopper 88 may deliver the pieces of material 1: directly into a feed chute 88 or into any suitable trough provided with a screw conveyer which would ultimately deliver the material into the feed chute 88 at one end of the drying cylinder 85. r

The cylinder 85 may be of any usual construction with its axis disposed at an incline to the horizontal and the fe d chute disposed at the elevated end of the cylinder and feeding the material through a suitable opening axially disposed in the head 88 of the rotary cylinder 85, whereby, as the drum is rotated, the ma-' terial will be fed more or less slowly down the incline of the cylinder and discharged from the cylinder through the lower end 81 thereof into a suitable container or onto a suitable conveyer, such as that illustrated at 88 in Fig. 2.

In order to carry off vapors arising from the high temperature heating of the material in the drum drier unit A, a suitable hood 88 may be disposed above said unit and provided with an exhaust fan 8| by which such vapors will be drawn upwardly through the hood and discharged at a suitable place remote to the drier.

The drum 85 may be rotated by any suitable means and may be heated or cooled in any suitable manner common to this type of drier for effecting the final drying or conditioning barrel drier the pieces do not attach themselves 15 one to another and remain separate whereby quick efficient drying of the material is readily effected by blowing air longitudinally through the barrel in which the pieces are receiving a more or less gentle tumbling or rolling action in the presence of the drying medium.

An important feature of drying plastic materials in accordance with the principles of the present invention resides in the preparation of the material in the initial drying step for the flnaldrying step of the process by reducing bulk of material to the individual pieces of uniform size, cross-sectional shape and area, which will permit moisture to be quickly drawn to the multitude of outside surfaces created by the formation of the individual pieces and from which the moisture will be quickly carried off or evaporated by the drying medium circulating between and around said pieces and contacting with said multitude of exposed surfaces.

Another important feature resides in the size of the uniform cross-sectional area of the pieces, the larger the area the longer the drying time and vice versa, and in practice it has been found that when the cross-sectional area of the pieces approximate .05 square inch the most efiicient drying is accomplished both as to uniformity of drying, quality, and time. With the initial drying and final drying being carried on in accordance with the process disclosed herein it has been found that it has been possible to reduce the drying time for a given bulk of material, which when dried in cake form in accordance with the usual practice would require approximately twenty-four hours to dry the cake through, to approximately twenty-five minutes, where the uniformly cross-sectional pieces were piled haphazardly in criss-cross or other irregular overlapping or latticed order on a perforated screen conveyer with'heated air circulating through the conveyer and the layer of material thereon; and wherein the cake would not dry evenly or uniformly at all parts thereof and causing some parts to be overdried while other parts of the cake were barely dried or underdried, the drying of the same quantity of material as contained in the cake, under the process of the present case, effected a complete uniform dryingof the material at a uniform rate, i. e. all pieces dried uniformly in the same length of time.

The size of the pieces is such that the pieces may be readily placed on the screen conveyer, as above noted, without any appreciable amount of the material sifting through the screen.

As shown in Fig. 13 of the drawings, the belt 50 may in some cases be supplanted by a plurality of repasting or reseating rolls Ma, Mb, ilo, Md, and a discharge chute 500 for reestablishing and/or maintaining the material in intimate contact with the walls of the grooves in the initial drying drum l, and for delivering the initially dried, shaped and otherwise prepared pieces of material to the apparatus for effecting the final drying step of the process.

Drum driers have been found to be highly eflicient for effectively and quickly driving out the larger portion of moisture from the material in a short period of time but where bone dryness or a state of drying approaching a bonedry condition is required the drum dried has been found to be rather inefiicient in that its hourly capacity is extremely low and limited, even in drums of relatively large diameters, but the drum drier has been found to be ideal for eifecting a preparation of plastic materials, i. e. a shaping to uniform size, setting of the size and shape and driving off the larger portion of the moisture from the material, for final dryingin apparatus where the drying medium can be circulated around the prepared pieces, but unless the pieces of material are uniformly sized cross-sectionally uniformity of drying both as to condition and time cannot be accomplished. The length of the pieces has no apparent efiect on either the condition or time of drying so long as the pieces are uniform cross-sectionally.

While specific structure has been disclosed for effecting the process of drying plastic materials in accordance with the present invention, other equivalent structures may be employed without departing from the spirit of the invention, in view of which only such limitations as may be dictated by the state of the art should be applied to the appended claims.

I claim:

1. A drier for plastic materials, comprising a heated drum provided with continuous circumferential grooves having imperforate bases and inwardly conver ing side walls disposed at an angle to each other from the bases to the tops of the respective grooves, means for initially pressing said material into said grooves and into contact with the walls thereof, and means for maintaining said material in contact with said walls.

2. A drier for plastic materials, comprising a heated drum provided with continuous circumferential. grooves having imperforate bases and inwardly converging side walls disposed at an angle to each other from the bases to the tops of the respective grooves, means for initially pressing said material into said grooves and into contact with the walls thereof, and means for repressing said material into contact with the groove walls.

3. A drier for plastic materials, comprising a heated drum provided with continuous circumferential grooves having imperforate bases and inwardly converging side walls disposed at an angle to each other from the bases to the tops of the respective grooves, means for initially pressing said material into said grooves and into contact with the walls thereof, means for repressing said material into contact with the groove walls, and means for maintaining said material in contact with the walls of the grooves.

4. A drier for plastic materials, comprising a heated drum provided wtih continuous circumferential grooves having imperforate bases and inwardly converging side walls disposed at an angle to each other from the bases to the tops of the respective grooves, a pasting roll for initially pressing said material into said grooves and into contact with the walls thereof, means for repressing said material into contact with the groove walls, and means for maintaining said material in contact with the walls of the grooves.

5. A drier for plastic materials, comprising a heated drum provided with continuous circumferential grooves having imperforate bases and inwardly converging side walls disposed at an angle to each other from the bases to the tops of the respective grooves, means for initially pressing said material into said grooves and into contact with the walls thereof, a roll for repressing said material into contact with the walls of the grooves, and means for maintaining the material in contact with the walls of the grooves.

6. A drier for plasic materials comprising a heated drum provided with continuous circumferential grooves having imperforate bases andinwardly converging side walls disposed at an angle to each other from the bases to the tops of the respective grooves, and a plurality of rolls operating against the periphery of the drum for pressing and repressing the material into intimate contact with the walls of said grooves.

7. A drier for plastic materials, comprising a heated drum provided with continuous circumferential grooves having imperforate bases and inwardly converging side walls disposed at an angle to each other from the bases to the tops of the respective grooves, means for initially pressing said material into said grooves and into contact with the walls thereof, means for repressing said material into contact with the groove walls, and a resilient means partially circumventing the drtma and traveling concurrently with the drum for maintaining the material in contact with the walls of the grooves.

8. A drier for plastic materials comprising a heated drum provided with continuous circumferential grooves having imperforate bases and inwardly convering side walls disposed at an angle to each other from the bases to the tops of the respective grooves, a roll for initially pressing the material into the grooves and into contact with the walls thereof, a second roll spaced from the ilrst roll for repressing the material into contact with the walls of the grooves, and a belt partially circumventing the roll and traveling concurrently therewith for maintainin the material in contact with the walls of the grooves.

9. A drier for plasic materials comprising a drum provided with continuous circumferential grooves of uniform cross section and having imperforate bases and inwardly converging side walls disposed at an angle to each other from the tops to the bases of said grooves respectively, means for pressing the material into and filling the grooves therewith cross-sectionally to form said material into long continuous strips having the uniform cross-sectional shape of said grooves throughout, means for heating the drum for driving moisture out of the strips of material in the grooves, means for repressing and maintaining the strips of material in the grooves in full cross-sectional contact with the walls of the grooves for initially drying and setting the material to the shape of the grooves, said heating causing said strips to shrink longitudinally and to break transversely into pieces of variable lengths while retaining the uniform cross-sectional shape of the grooves, means for removing the set and partially dried pieces from said grooves while still retaining the uniform crosssectional shape of the grooves.

10. The process of drying plastic material which consists in pasting the material into suitable continuous linear cavities of predetermined uniform cross-section to form the material into strips of uniform cross-section corresponding to the cross-sectional shape of said cavities, heating the walls of said cavities to drive out moisture from and to set the shape of the strips, said heating causing the strips to shrink longitudinally and to break transversely into pieces having a uniform cross-section corresponding to that of said cavities, maintaining the pieces in intimate contact with the heated walls of the cavities throughout the whole of said setting operation, removing the set pieces from said cavities, and subsequently drying the set pieces in the presence of a circulating drying medium.

11. The process of drying plastic material which consists in pasting the material into suitable cavities of predetermined uniform crosssection, heating the walls of said cavities to drive out moisture from and to set the shape of the material into pieces having a uniform crosssection corresponding to that of said cavities, repressing the material in said cavities to insure intimate contact between the material and the heated walls of said cavities when the material loses contact with said walls as by the escape of generated vapor from the material and the shaping cavities, maintaining the pieces in intimate contact with the heated walls of the cavities during said setting, removing the set pieces from said cavities. and subsequently drying the set pieces in the presence of a circulating drying medium.-

12. The process of drying plastic material which consists in pasting the material into suitable cavities of predetermined uniform crosssection, heating the walls of said cavities to drive out moisture from and to set the shape of the material into pieces having a uniform crosssection corresponding to that of said cavities, repressing the material in said cavities to insure intimate contact between the material and the heated walls of said cavities when the material loses contact with said walls as by the escape of generated vapor from the material and the shaping cavities, maintaining the pieces in intimate contact with the heated walls of the cavities during said setting, removing the set pieces from said cavities, spreading the set shaped pieces in a layer on a suitable support in a manner to provide space around and between said pieces, and circulating a drying medium through the layer around, between and in contact with the exposed surfaces of said pieces.

ALPHEUS O. HURX'IHAL. 

